Birmingham: With inspirational skipper Michael Clarke ruled out due to injury, two-time defending champions Australia are looking more vulnerable than ever as they gear up for their Champions Trophy Group A opener against confident Ashes rivals England on Saturday.

Their patchy form aside, Aussies have a major worry to deal with as Clarke's long-standing back problem has flared up once again, ruling him out for tomorrow's game while casting a shadow of doubt on his participation in the matches after that.

The inspirational skipper is a crucial cog in the Australian scheme of things given that his batting form has more often than not been the difference between a win and loss for the team in the past few months.

England, on the other hand, would be looking to flourish in familiar conditions even though they endured an ODI series loss to a rather weak New Zealand just before the Champions Trophy.

But an overall assessment of their ODI stats would reveal that since 2010, England have won 23 and lost only 11 of the 37 matches they have played at home.

A look at the team sheets gives a fair idea of just why the hosts would be the favourites on Saturday.

Australia, a team well past its glory days, is struggling to cope with what has been a tormenting transitional phase.

The side's batting has looked brittle and this frailty was most recently exposed in the warm-up match against India last week when, in the absence of Clarke, they were bowled out for just 65 runs while a chasing a steep 309.

Given the situation, it would be absolutely vital for Australia that Clarke returns to full fitness as soon as possible.

The team would also be looking at imposing all-rounder Shane Watson to do quite a lot of scoring after a fine IPL stint with the Rajasthan Royals.

England, in contrast, look a settled squad even though the absence of an injured Kevin Pietersen could hurt them quite a bit.

Bulk of the scoring is likely to be done by the top-order trio of Ian Bell, Alastair Cook and Jonathan Trott with the likes of Joe Root and Jos Buttler expected to build on the solid starts.

The bowling line-up is impressive with the formidable pace trio of James Anderson, Steven Finn and Stuart Broad ably supported by skillful spinner Graeme Swann.